Turbocharged internal combustion engines utilize outgoing exhaust gas from the engine to pressurize intake air for combustion. In general terms, pressurizing the intake air increases the quantity of air entering the engine cylinders during an intake stroke, and allows more fuel to be utilized to increase available engine output torque and power. Turbochargers will often operate effectively over a reasonably broad operating range of speeds and loads for the engine to which they are coupled. Under certain conditions, however, disruptions to the flow of gases through turbochargers can occur and deleteriously affect engine operation. In particular, a phenomenon known in the art as surge occurs when there is localized or complete reversal of the flow of gases through a turbocharger, notably the compressor side. Surge can occur where there are relatively rapid speed changes in the engine coupled with certain pressure conditions in the compressor and/or turbine of a turbocharger, causing a disparity between compressor pressure and intake manifold pressure which results in reversal of flow. Certain other conditions can also destabilize compressor flow, causing surge and resulting in the engine either being starved for air, over-fueled, or experience some other problem which can eventually lead to turbocharger or engine damage or failure.
U.S. Pat. No. 6,408,624 to Books et al. is directed to a system for controlling transient compressor surge in a turbocharged engine, and proposes a control circuit responsive to an engine operating parameter such as engine speed to determine a fueling limit that is made higher under certain engine operating conditions or made lower under others, to avoid turbocharger compressor surge conditions. While the strategy proposed by Books et al. may be useful, it is not without drawbacks, among them it appears to be a relatively complicated strategy that is directed specifically to one type of turbocharger surge phenomenon.